The Australian Homelessness Monitor 2018 report, released on Tuesday, shows that while the overall number of homeless people decreased by 8 per cent in the territory over the five-year period, the number of people sleeping rough grew from 28 to 54.

The rise in the number of rough sleepers came as ACT government spending on homelessness services fell by nearly $5 million, down from $25.3 million in 2012-13 to $20.7 million last financial year.

The government's investment in social housing dropped by 80 per cent over the same period, forking out just $6.7 million in 2016-17 after spending $33.9 million in 2012-13.

University of NSW Professor Hal Pawson, who co-wrote the new report, said the increase in rough sleepers was a real concern.

"It's the sharp end of the problem. That's when things get as rough as they can get," Professor Pawson said.

"Just re-housing people off the streets - while it's urgent and something that needs to be done - won't be a lasting solution unless there are wider changes put in place."

While the ACT's population increased by 8 per cent between the 2011 and 2016 census surveys, the number of social houses increased by just 4 per cent.

Professor Pawson said that, combined with a lack of affordable rental homes, was making life hard for Canberrans on low incomes.

"Homelessness is a barometer of other things that are going on, like the labour market and housing market stress," Professor Pawson said.

"Social housing has been growing, so three cheers for that, but it's only growing at half the rate of the population.

"Then you've got growing numbers of people competing for low-cost rental housing, and that pool [of houses] isn't growing with them."

ACT Housing Minister Yvette Berry said the funding cuts came after the federal government changed homelessness funding for states and territories to a per capita rate as part of the National Affordable Housing Agreement.

Under that agreement, Commonwealth spending on homelessness in the ACT has fallen, with the federal government chipping in $23.9 million in 2016-17, down from $27.8 million in 2012-13.

"Housing ACT is in regular contact with about 60 per cent of rough sleepers and provides support to help them transition off the street," Ms Berry said.

"It is also working with its service partners to reach and assist the other 40 per cent, who are typically more endemically homeless and less likely to engage with government support."

Ms Berry said the ACT government had been working with the Commonwealth and other state and territory governments to develop a new national agreement, and while no additional funding had yet been provided, the ACT was expected to receive $25.8 million in 2018-19 under the current agreement.

She said the overall decline in homelessness showed the ACT's specialist homelessness sector was effective, with the 8 per cent reduction in the number of homeless people in the territory coming at a time when national figures showed an increase of 13.7 per cent across Australia.

The Homelessness Monitor report is the first of its kind in Australia, and is based on data from a range of sources including the Australian Bureau of Statistics, Productivity Commission and Australian Institute of Health and Welfare. It was written by researchers from the University of NSW and University of Queensland, with funding support from Melbourne-based community agency Launch Housing.